Effective thermal management is a concern in many industries and for various types of consumer goods. For example, heat build-up in a computer's central processing unit (CPU) can degrade the computer's performance just as heat build-up (or “heat soak”) in an automobile's brakes or engine can degrade the automobile's performance. Many machines and devices have performance limits that are often defined by how well heat developed during operation is managed. Such heat build-up is often a byproduct of power transmission and use.
Some common thermal management techniques rely on convective heat transfer. Convective heat transfer, often referred to simply as convection, is the transfer of heat from one place to another by the movement of fluids. Convection is usually the dominant form of heat transfer in liquids and gases. Convection can be “forced” by movement of a fluid by means other than buoyancy forces (for example, a water pump in an automobile engine). For machinery and electronic components, convective cooling is typically employed.
A heat pipe or heat pin is a heat-transfer device that combines the principles of both thermal conductivity and phase transition to efficiently manage the transfer of heat between two solid interfaces. At the hot interface of a heat pipe a liquid in contact with a thermally conductive solid surface turns into a vapor by absorbing heat from that surface. The vapor then travels along the heat pipe to the cold interface and condenses back into a liquid—releasing the latent heat. The liquid then returns to the hot interface through either capillary action or gravity, and the cycle repeats. Consumer electronics such as personal computers often utilized heat pipes for cooling processing units.
Since they rely on fluids as media to transport heat, such convective and heat-pipe cooling techniques can present issues relating to management (e.g., containment and pumping) of the fluids, and may not be appropriate for some applications.
Thermoelectric cooling employs the Peltier effect to create a heat flux between the junction of two different types of materials. The Peltier effect is the presence of heating or cooling at an electrified junction of two different conductors and is named for French physicist Jean Charles Athanase Peltier, who discovered it in 1834. When a current is made to flow through a junction between two conductors A and B, heat may be generated (or removed) at the junction. A Peltier cooler, heater, or thermoelectric heat pump is a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current. Such an instrument is also called a Peltier device, Peltier heat pump, solid state refrigerator, or thermoelectric cooler (TEC). They can be used either for heating or for cooling (refrigeration) although in practice the main application is cooling. It can also be used as a temperature controller that either heats or cools.
Thermoelectric cooling is reliant on supplied electricity for the cooling effect and consequently may not be desirable for some applications.